Piezo-electric apparatus for acting on an optical path

ABSTRACT

An apparatus for acting on an optical path, includes an at least partly opaque lever, and a bearance fulcrum about which at least a part of the lever is slewable at least partly in and out of the optical path by the use of a piezo-electric force.

This application is the National Stage of International Application No.PCT/EP02/00581, International Filing Date, Jan. 22, 2002, whichdesignated the United States of America, and which internationalapplication was published under PCT Article 21(2) as WO Publication No.WO 03/062898 A1.

BACKGROUND OF THE INVENTION

When using optical signals traveling an optical path it is oftennecessary to interrupt or damp the optical signal. Therefore, the priorart provides so-called shutters to at least partly block an opticalpath, thereby interrupting or damping the optical signal traveling thepath. These known shutters are moved by electromagnetic forces.

SUMMARY OF THE INVENTION

It is an object of the invention to provide improved acting on anoptical path of an optical signal.

The object is solved by the independent claim.

An advantage of the present invention is that the use of the levereffect makes it possible to use piezo-electric forces for moving thelever to provide a shutter suitable for the demands of optical devices.So far, piezo-electric forces, e.g. provided by a piezo-electricelement, were not able to provide a sufficient tilting angle of thepiezo-electric element when using piezo-electric elements the size ofwhich can be accepted for a shutter to be used in optical devices. i.e.elements having sufficient tilting angle were to big to be integrated inoptical devices and elements having the desired compactness were notable to provide a sufficient tilting angle.

Moreover, the use of piezo-electric forces does not only shrink the sizeof the shutter but does also shrink the amount of energy necessary tomove the lever used as a shutting element of a shutter according to theinvention compared to the electromagnetic energy used in the prior artfor moving a shutter.

In a preferred embodiment of the invention there is provided apiezo-electric element to exert the piezo-electric force on one end ofthe lever. By using such an element and by letting it act on the end ofthe lever it is possible to use the advantages of piezo-electric forcesas described above and simultaneously enhance the stroke of the lever.

Preferably, the lever comprises a first lever arm on one side of thefulcrum and a second lever arm on the other side of the fulcrum, thepiezo-electric element being connected to an end of the first lever armremote of the fulcrum. Thereby, the effect of the enhancement of thestroke of the lever is maximized.

In another preferred embodiment the end of the lever being connected toone end of the piezo-electric element which is slewable whereas anotherend of the piezo-electric element is fixed relative to the apparatus.This also maximizes the stroke of the lever.

In a further preferred embodiment the end of the piezo-electric elementbeing at least partly articulated in a seat in the first lever arm.Thereby, it is possible to provide a little play of the end of theelement in the lever to further enhance the lever action caused by thepiezo-electric element.

It is further preferred to provide two catches as a lever stop and beingpositioned to be able to separable lock the lever at least partly in andout of the optical path. Thereby, with each single activation of thepiezo-electric element the lever changes its position. Therefore, thelever arrangement is a bistable system and the lever has always a knownand defined position making the work of an accordingly constructedshutter more predictable.

Other preferred embodiments are shown by the dependent claims.

It is clear that the invention can be partly embodied or supported byone or more suitable software programs, which can be stored on orotherwise provided by any kind of data carrier, and which might beexecuted in or by any suitable data processing unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and many of the attendant advantages of the presentinvention will be readily appreciated and become better understood byreference to the following detailed description when considering inconnection with the accompanied drawing. The components in the drawingare not necessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention.

FIG. 1 shows a cross section of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cross section of a shutter 1 according to an embodimentof the present invention. Shutter 1 has a housing 2. Mounted in thehousing 2 is an elongated mounting plate 4 having two stands 6 a and 6 bconnected with a base plate 2 a of the housing 2. A groove 8 is providedin the left stand 6 a. In the groove 8 there is clamped an end 9 of abimorph type piezo-electric plate 10 connected to a not shown voltagesupply. The other end 11 of the plate 10 is freely slewable. The freelength l of the piezoelectric plate is 28.4 mm. The clamped length k ofthe plate is 2.5 mm. By changing the voltage applied to the plate 10 theposition of the plate 10 can be changed from the position having thecenter line 12 to the position having the center line 14 by using thepiezo-electric characteristic of the piezo-electric plate 10.Alternatively, the bimorph type piezo-electric plate 10 can be supportedor replaced by a multilayer bender actuator (not shown), e.g. amultilayer bender piezoelectric translator actuator of the PL series ofPhysik Instrumente (PI) GmbH&Co, Auf der Roemerstrasse, D-76228Karlsruhe/Palmbach.

A stay 16 is extending from the mounting plate 4 opposite to the stand 6b. Stay 16 has a recess 18 providing a bedding for an arbor 20.Connected to the arbor 20 is a rod 22 of opaque and non reflectivematerial. The arbor 20 provides a bearance fulcrum for the rod 22,thereby arbor 20 and rod 22 constitute a lever arrangement with the rodbeing a lever. The lever 22 has a first lever arm 24 on one side (on theright in FIG. 1) of the fulcrum 20 and a second lever arm 26 on theother side (on the left in FIG. 1) of the fulcrum 20. The piezo-electricplate 10 is connected to an end 28 of the first lever arm 24 remote ofthe fulcrum 20. The end 11 of the piezo-electric plate 10 is articulatedin a seat 30 provided in the first lever arm 24.

Activating the piezo-electric force of the plate 10 the plate 10 bendsdown from the position with center line 12 into position with centerline 14. Since the plate 10 is seated with its end 11 in the seat 30 ofthe first lever arm 24 the plate pulls down the first lever arm 24thereby slewing and rising the second lever arm 26 from a positionshutting an optical path 32 and shown with solid lines about an angleα=10° into a position opening the optical path 32 and shown with dottedlines.

With the free length l=28.4 mm a stroke m of 3 mm can be provided by theshown shutter 1. Therefore, optical signals, e.g,. laser beams, having acore thickness 32 of up to 1.5 mm and a corresponding diffuse thicknessof up to 3 mm can be interrupted completely.

The shutter 1 further comprises a not shown measuring device formeasuring the stewing angle α of the lever 22 by a not shown wire-straingauge bonded to the piezo-electric plate 10, a not shown comparatorconnected with the measuring device for comparing the measured value ofthe slewing angle α with a predetermined value of the slewing angle α,and a not shown controller connected with the piezo-electric plate 10for adjusting the piezo-electric force provided by the piezo-electricplate 10 when the comparator has detected a difference between themeasured value and the predetermined value of the stewing angle α.

Two not shown catches are positioned to be able to separable lock thesecond lever arm 26 at least partly in and out of the optical path 32.The piezo-electric force of the piezo-electric plate 10 is strong enoughto release the lever 22 from each catch and to switch the lever 22between the two catches.

1. An apparatus for acting on an optical path, comprising: an at leastpartly opaque or non-transmissive lever; a bearance fulcrum about whichat least a part of the lever is slewable at least partly in and out ofthe optical path by the use of a piezo-electric force; and apiezo-electric element to exert the piezo-electric force on one end ofthe lever, wherein the lever comprises a first lever arm on one side ofthe fulcrum and a second lever arm on the other side of the fulcrum, thepiezo-electric element being connected to an end of the first lever armremote of the fulcrum.
 2. The apparatus of claim 1, wherein thepiezo-electric element comprises an end being a least partly articulatedin a seat in the first lever arm.
 3. The apparatus of claim 1, whereinthe piezo-electric element being of bimorph type.
 4. The apparatus ofclaim 1, wherein the end of the lever being connected to one end of thepiezo-electric element which is slewable whereas another end of thepiezo-electric element is fixed relative to the apparatus.
 5. Theapparatus of claim 1, wherein at least a part of the second lever armserves as the part of the lever slewable at least partly in and out ofthe optical path.
 6. The apparatus of claim 1, further comprising atleast one catch in which the lever can be separable locked in at leastone predetermined position.
 7. The apparatus of claim 6, wherein twocatches being positioned to be able to separable lock the lever at leastpartly in and out of the optical path.
 8. The apparatus of claim 7,wherein the piezo-electric force of the piezo-electric element beingstrong enough to release the lever from each catch and to switch thelever between the two catches.
 9. The apparatus of claim 1, furthercomprising: a measuring device for measuring the slewing angle (a) ofthe lever, a comparator connected with the measuring device forcomparing the measured value of the slewing angle (a) with apredetermined value of the slewing angle (a), and a controller connectedwith the piezo-electric element for adjusting the piezo-electric forcewhen the comparator has detected a difference between the measured valueand the predetermined value of the slewing angle (a).
 10. The apparatusof claim 9, wherein the measuring device comprises a wire-strain gaugebonded to the piezo-electric element.